In the chick embryo, the acellular portion(s) of the primary corneal stroma is composed of a series of layers or plies, each composed of numerous striated fibrils which are equally spaced from one another. Fibrils in alternate layers are arranged essentially orthogonal to one another with some of the layers in each eye being precisely rotated a few degrees in a clockwise direction. Our recent observation that the primary corneal stroma is composed of two genetically different collagens, type I and type II, both of which are synthesized by the corneal epithelium, has raised a number of questions as to how these molecules are themselves assembled, and how they may interact in the formation of the primary stroma. We propose first to establish the role that collagen precursor chains play in the correct molecular assembly of the two collagen types that are found in the primary stroma. We also will investigate whether post-translational glycosylation of the two types of collagen might be involved in determining the precise fibril diameter found in the cornea. Then, as an initial step in determining the possible role(s) these different collagens play in corneal morphogenesis, we will establish the temporal sequence through which the corneal epithelium acquires the production of the two different collagens and see whether changes in the synthesis of these two molecules correlate with any of the major morphogenetic events which occur during corneal development, e.g., orthogonality, rotation, fibroblast invasion. Lastly, we will use biochemical probes to further determine whether the types of collagens synthesized, or whether the synthesis of glycosaminoglycans (GAG) is involved in the arrangement of the lamellae in the primary stroma.